Catalysts are used in internal combustion engines for emissions control of toxins and/or regulated emissions from the exhaust stream of the engine. For example, a catalyst used in a catalytic converter is commonly used in motor vehicle exhaust systems and other engine systems. The catalyst reduces the activation energy required for chemical reactions wherein combustion by-products are converted to less-toxic or non-regulated substances. Typically, the catalyst is connected to an exhaust flow of the engine to perform the desired conversion before emitting the exhaust from the engine to the atmosphere.
A close-coupled catalyst (CCC) can be used in some engines for emissions control. The close coupled catalyst is used to convert carbon monoxide (CO) and hydrocarbons (HC) to carbon dioxide and water vapor. The oxidation of these hydrocarbons is an exothermic reaction, which if harnessed, can also provide the energy required to reduce soot and particulate matter (PM) to ash. In some of these applications, a doser of the exhaust system of the engine can be located upstream in the exhaust flow and “closely coupled” to the inlet of the catalyst. The doser can introduce diesel fuel into the exhaust in a controlled manner which is then oxidized by the close coupled catalyst, generating enough heat to burn soot trapped in a downstream particulate filter. Coupling the catalyst closer to the doser gives greater oxidation time for the HC, increasing the effectiveness of the conversion process. However, coupling the catalyst too close to the doser can prevent the fuel from being sufficiently mixed in the exhaust stream, also reducing effectiveness.
While the addition of a close coupled catalyst provides a solution to certain emissions requirements, the appending of additional components to the engine creates its own set of problems. Some engine configurations are not well configured for alternate placement and support of a close-coupled catalyst. For example, hanging a catalyst element from the doser without any support loads too much weight at one end of the doser. However, there is often little room to place a support for the catalyst. In addition, placement of the catalyst may be in different locations depending on the application of the engine, especially in the plethora of vehicle chassis which each have different available space, clearance, and mounting requirements. Furthermore, overly constraining the catalyst to the block and/or other engine components may lead to failure of the system, such as cracking of component parts and gas leakage, due to thermal expansion of parts, vibration of the engine, installation preload, and/or other root causes and/or other behavioral characteristics.
Accordingly, a system and method for providing a stable and versatile mounting of a close-coupled catalyst for an engine would be desirable in many applications.